Nielsen estimates that NBCSN averaged 4.137 million viewers from 8:01-11:16 p.m. ET — making it the most-watched cable network in primetime. The game, won by the Kings, peaked from 10:30-10:45 p.m. ET with about 5.5 million viewers.

It did a 1.5 national rating in adults 18-49, making it the No. 2 cable program of the day, behind only HBO’s “Game of Thrones.”

Sunday’s deciding game of a series featuring the previous two Stanley Cup champs tops the previous record for a non-Cup Final NHL game, which was Game 6 of the 1996 Eastern Conference Final between the Florida Panthers and Pittsburgh Penguins (4.049 million).

It also ranks higher than any Stanley Cup Final to air on NBCSN, besting last year’s pair of games, which averaged about 4 million.

The 22.7 household rating in Chicago for Sunday’s game is the top rating for a Blackhawks game ever on NBCSN. And in Los Angeles, the 4.8 rating is the best metered-market overnight for a conference final game, according to Nielsen.

In New York, whose Rangers were anxious to see whom they would meet in the Cup Final, the game did a 3.7 rating, its best ever on NBCSN ever for a non-Stanley Cup Final game that didn’t include a New York team.

Through three rounds, the 2014 Stanley Cup Playoffs are the most-watched in 17 years. NBC, NBCSN and CNBC have combined to average 1.187 million viewers for 86 games, up 11% from the 1.074 million for last year’s 78 games. This is a higher pre-Cup Final average for the NHL Playoffs since Fox, ESPN and ESPN2 combined to average 1.237 million in 1997.

Game 1 of the Stanley Cup Final between the Kings and Rangers is set for Wednesday night in Los Angeles. NBC will air the first two games of the series, before NBCSN takes over for Games 3 and 4.